Roller hemming apparatus and roller hemming method

ABSTRACT

A roller hemming apparatus includes: a cylindrical roller supported rotatably on a main body; a first position adjusting mechanism for adjusting a first position of the roller in a direction which is perpendicular to a rotating axis direction thereof; a second position adjusting mechanism for adjusting a second position of the roller in the rotating axis direction; and a control unit for controlling the first and second position adjusting mechanisms. The control unit adjusts the first position by controlling the first position adjusting mechanism to abut the roller with a third position which is apart from a bending point of the flange, and the control unit adjusts the second position by detecting a load acting on the roller in an axial direction thereof as a drive load, calculating a difference between the drive load and a given master load, and controlling the second position adjusting mechanism according to the difference.

This application claims priority from Japanese Patent Application No. 2009-140977, filed on Jun. 12, 2009, the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present disclosure relates to a roller hemming apparatus and a roller hemming method, and more particularly to a roller hemming apparatus and a roller hemming method for hemming a flange which is formed on a workpiece.

DESCRIPTION OF RELATED ART

Body panels of a motor vehicle such as a door panel, a side panel or a hood are made up of an outer panel and an inner panel which are integrated with each other.

A process of integrating an outer panel and an inner panel includes, for example, a marriage step of superposing an inner panel on an outer panel having a flange formed so as to extend upwards and a hemming step of bending the flange of the outer panel inwards thereof by a roller hemming apparatus.

Japanese Patent Application Publication No. JP-A-2008-023587 discloses a related-art roller hemming apparatus including a main body, a roller supported rotatably on the main body, and a moving mechanism provided on the main body for moving the roller in a direction of a rotating axis thereof.

In the related-art roller hemming apparatus, a position of the roller in the rotating axis direction is adjusted in advance according to property of the outer panel. Then, by moving the roller hemming apparatus along an end edge of the outer panel, the flange of the outer panel is pressed by the roller so as to bend the flange inwards of the outer panel.

Incidentally, there may be caused a slight variation in material or height of flanges of outer panels used in the hemming step described above lot by lot. As this occurs, since deformation resistance of flanges varies, a spring-back amount of resulting hemmed flanges also varies, leading to vary angles of hemmed flanges.

SUMMARY OF INVENTION

Illustrative aspects of the present invention provide a roller hemming apparatus in which a flange shape of a workpiece after hemming can be constant, and a roller hemming method.

According to a first aspect of the invention, a roller hemming apparatus for hemming a flange formed on a workpiece, comprising: a main body; a cylindrical roller supported rotatably on the main body; a first position adjusting mechanism for adjusting a first position of the roller with respect to a direction which is perpendicular to a rotating axis direction of the roller; a second position adjusting mechanism for adjusting a second position of the roller with respect to the rotating axis direction; and a control unit for controlling the first position adjusting mechanism and the second position adjusting mechanism, wherein the control unit adjusts the first position of the roller by controlling the first position adjusting mechanism to bring the roller into abutment with a third position which is spaced by a given distance apart from a bending point of the flange, and wherein the control unit adjusts the second position of the roller by detecting a load acting on the roller in an axial direction of the roller as a drive load, calculating a difference between the drive load and a given master load, and controlling the second position adjusting mechanism according to the difference

Other aspects and advantages of the invention will be apparent from the following description, the drawings and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall perspective view showing a roller hemming system using a roller hemming apparatus according to an exemplary embodiment of the invention;

FIG. 2 is an enlarged perspective view showing a working table of the roller hemming system;

FIG. 3 is a perspective view showing the roller hemming apparatus;

FIG. 4 is a diagram showing a configuration of a control means of the roller hemming apparatus;

FIG. 5 is a flowchart showing operations for adjusting a position of a hemming roller of the roller hemming apparatus with respect to a rotating axis direction;

FIG. 6 is a diagram showing an operation in which the hemming roller of the roller hemming apparatus is brought into abutment with a flange or a workpiece;

FIG. 7 is another diagram showing an operation in which the hemming roller of the roller hemming apparatus is brought into further abutment with the flange of the workpiece; and

FIG. 8 is a further diagram showing an operation in which the hemming roller of the roller hemming apparatus is brought into still further abutment with the flange of the workpiece.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an exemplary embodiment of the invention will be described based on the drawings.

FIG. 1 is an overall perspective view showing a roller hemming system 1 using a roller hemming apparatus 10 according to an exemplary embodiment of the invention.

The roller hemming system 1 includes a working table 30 on which an outer panel 20 as a workpiece is placed, a robot 40 placed in a vicinity of the working table 30, and a controller 50 for controlling the robot 40.

The outer panel 20 is such as to be formed by bending a panel and includes a flat plate-like base portion 21 and a flange 22 which is formed on a circumferential edge of the base portion 21.

FIG. 2 is an enlarged perspective view showing the working table 30.

The working table 30 includes a support 31 (FIG. 1) provided on a floor and a die 32 supported on the support 31.

A circumferential edge portion of an upper face of the die 32 is made higher than a central portion thereof, whereby a riser plane 321 is formed along the circumferential edge portion. The outer panel 20 is disposed so that the flange 22 is brought into abutment with the riser plane 321.

A groove 322 is formed on a lower face of the die 32 so as to extend along the circumferential edge portion. Accordingly, the groove 322 is made parallel to a direction in which the flange 22 of the outer panel 20 extends.

The robot 40 includes a base portion 41 fixed to the floor and a robot arm 42 which is provided on the base portion 41 for adjusting a position and a posture of the roller hemming apparatus 10 in a three-dimensional space.

FIG. 3 is a perspective view showing the roller hemming apparatus 10.

The roller hemming apparatus 10 is attached to a distal-end flange 42 a of the robot arm 42. The roller hemming apparatus 10 includes a main body 11, a hemming roller 12 as a cylindrical roller supported rotatably on the main body 11, a pressing mechanism 13 as a first position adjusting mechanism which is provided on the main body 11 for adjusting a position of the hemming roller 12 in a direction which is perpendicular to a rotating axis direction thereof, and a pushing mechanism 14 as a second position adjusting mechanism which is provided on the main body 11 for adjusting a position of the hemming roller 12 in the rotating axis direction.

The main body 11 includes an outer housing 15 in which an elongated hole portion 15 a is formed, a hemming roller supporting portion 16 which projects from the hole portion 15 a in the outer housing 15 to support rotatably the hemming roller 12, the pushing mechanism 14 for adjusting a position of the hemming roller supporting portion 16, a circular disc-like guide roller 17 which is provided so as to confront the hemming roller 12, and a roller supporting portion 18 which projects from the hole portion 15 a in the outer housing 15 to support rotatably the guide roller 17.

The guide roller supporting portion 18 includes a supporting portion main body 18 a for supporting the guide roller 17 rotatably and an arm 18 b which projects from the hole portion 15 a in the outer housing 15 to support the supporting portion main body 18 a rotatably about a rotating axis which is directed perpendicular to the rotating axis of the hemming roller 12. Accordingly, a rotating axis of the guide roller 17 becomes parallel to the rotating axis of the hemming roller 12 or is inclined relative to the rotating axis of the hemming roller 12.

A distal end face 121 of the hemming roller 12 is chamfered so as to have two tapering surfaces as the first position adjusting mechanism (refer to FIG. 6). The two tapering surfaces are made up of a first tapering surface 122 which is formed on a distal end side of the hemming roller 12 and a second tapering surface 123 which is formed closer to a proximal end side of the hemming roller 12 than the first tapering surface 122 and whose inclination angle relative to the rotating axis is smaller than that of the first tapering surface 122.

The rotating axis of the hemming roller 12 extends in a direction in which the hemming roller 12 projects from or retreats into the hole portion 15 a in the outer housing 15.

The pushing mechanism 14 includes a servo motor 141, a ball screw connected to a rotating shaft (not shown) of the servo motor 141, a nut portion, not shown, which is fixed to the hemming roller supporting portion 16 and which screws on the ball screw, a load detection sensor 142 for detecting a torque as a drive load acting on the servo motor 141, and a position detection sensor 143 for detecting an axial position of the hemming roller 12.

This pushing mechanism 14 moves the hemming roller supporting portion 16 in the direction in which the hemming roller supporting portion 16 projects from or retreats into the outer housing 15 by driving the servo motor 141 to rotate the ball screw. Namely, the pushing mechanism 14 moves the hemming roller supporting portion 16 along the rotating axis direction of the hemming roller 12.

The pressing mechanism 13 adjusts a space between the hemming roller 12 and the guide roller 17 by moving at least one of the hemming roller supporting portion 16 and the guide roller supporting portion 18.

The guide roller 17 can fit in the groove 322 provided in the die 32 at a circumferential edge thereof.

FIG. 4 is a diagram showing a configuration of the controller 50.

The controller 50 is provided with a Central Processing Unit (CPU) for processing various functions, and a memory for storing tables which stores data and programs which executes various functions. The controller 50 controls the robot arm 42 of the robot 40 and also controls the roller hemming apparatus 10.

The controller 50 includes an arm control unit 51 for controlling the robot arm 42 of the robot, a pressure control unit 52 for controlling the pressing mechanism 13, a position command value data table 53 for storing a command value for a position of the hemming roller 12 with respect to the rotating axis direction thereof as a position command value, a pushing control unit 54 for controlling the servo motor 141 of the pushing mechanism 14 based on the position command value stored in the position command value data table 53, a master load data table 55 for storing a torque reference value as a master load, a differential load calculation unit 56 for calculating a difference between a toque detected by the load detection sensor 142 and the torque reference value stored in the master load data table 55, a position command value calculation unit 57 for calculating a position command value according to the difference calculated at the differential load calculation unit 56, a position command value changing unit 58 for causing the position command value calculated at the position command value calculation unit 57 to be stored in the position command value data table 53, and a master load changing unit 59 for calculating a new torque reference value according to the difference calculated at the differential load calculation unit 56 to store the new torque reference value in the master load data table 55.

The pushing control unit 54 reads out the position command value stored in the position command value data table 53 and controls a current to be supplied to the servo motor 14 while monitoring the position of the hemming roller 12 by the position detection sensor 143 so that the hemming roller 12 is located in a given position which matches the position command value.

The differential load calculation unit 56 calculates a torque difference by reading out the torque reference value stored in the master load data table 55 and subtracting the torque reference value from the torque detected by the load detection sensor 142.

The position command value calculation unit 57 increases the position command value in the rotating axis direction of the hemming roller 12 when the difference calculated by the differential load calculation unit 56 is positive.

Namely, when the torque detected by the load detection sensor 142 is larger than the torque reference value, it is determined that the deformation resistance of the outer panel 20 is large, and then the position command value calculation unit 57 increases the position command value so as to cause the hemming roller 12 to project from the outer housing 15.

When the torque detected by the load detection sensor 142 is larger than the torque reference value, that is, when the difference calculated by the differential load calculation unit 56 is positive, the master load changing unit 59 sets the torque detected by the load detection sensor 142 as a new torque reference value and causes the new torque reference value to be stored in the master load data table 55.

FIG. 5 is a flowchart showing operations for adjusting the position of the hemming roller 12 in the rotating axis direction thereof.

In step S1, the pushing control unit 54 reads out the position command value stored in the position command value data table 53. Then, by controlling the current that is supplied to the servo motor 141 provided in the pushing mechanism 14 so that the hemming roller 12 is located in the given position which matches the position command value, the hemming roller 12 is caused to move towards the given position in the rotating axis direction thereof.

In step S2, the pushing control unit 54 determines whether or not the position of the hemming roller 12 detected by the position detection sensor 143 has reached the given position.

If the determination is YES, the flow of operations proceeds to step S4, whereas if the determination is NO, the flow of operations proceeds to step S3.

In step S3, the pushing control unit 54 increases the current to be inputted into the servo motor 141 provided in the pushing mechanism 14, and the flow of operations returns to step S1.

In step S4, since the hemming roller 12 has reached the given position which matches the position command value, the differential load calculation unit 56 calculates a difference between the torque detected by the load detection sensor 142 and the torque reference value stored in the master load data table 55.

In step S5, the position command value calculation unit 57 determines whether or not the difference calculated at the differential load calculation unit 55 is positive. If the determination is YES, the flow of operations proceeds to step S6, whereas if the determination is NO, the flow of operations ends.

In step S6, since the difference calculated at the differential load calculation unit 56 is positive, it is determined that the deformation resistance of the outer panel 20 is high, and then the position command value calculation unit 57 increases the position command value, and the position command value changing unit 58 causes the increased position command value to be stored in the position command value data table 53.

In step S7, the master load changing unit 59 sets the torque detected by the load detection sensor 142 as a new torque reference value and causes the new torque reference value to be stored in the master load data table 55, and the flow of operations returns to step S1.

Next, the operation of the roller hemming system 1 will be described.

The roller hemming system 1 will operates as will be described below.

In an initial state, the outer panel 20 is disposed on the die 32 so that the flange 22 is in abutment with the riser plane 321. Note that an inner panel, not shown, is disposed on the outer panel 20.

First, the robot arm 42 of the robot 40 is controlled by the arm control unit 51 of the controller 50 so that the roller hemming apparatus 10 approaches the working table 30 so as to allow the guide roller 17 of the roller hemming apparatus 10 to fit in the groove 322 on the lower face of the die 32.

Next, the pressing mechanism 13 is controlled by the pressure control unit 52 of the controller 50 so that the space between the hemming roller 12 and the guide roller 17 gets narrower so as to allow the hemming roller 12 to be disposed on the circumferential edge portion on the upper face of the die 32.

Next, the hemming roller 12 is caused to project from the outer housing 15 by the pushing mechanism 14, and as shown in FIG. 6, the distal end face 121 of the hemming roller 12 is brought into abutment with the flange 22 of the outer panel 20.

Next, the hemming roller 12 is caused to further project from the outer housing 15 by the pushing mechanism 15, and as shown in FIG. 7, a corner portion between the distal end face 121 of the hemming roller 12 and the first tapering surface 122 is brought into abutment with the flange 22 of the outer panel 20 so as to press the flange 22. The abutment position of the hemming roller 12 is located in a position which is spaced by a given distance B₁ apart from a bending point A of the flange 22.

Next, when the guide roller 17 moves along the groove 322, the hemming roller apparatus 10 moves along the flange 22. Then, the flange 22 is pressed to be bent by the hemming roller 12.

The position of the hemming roller 12 is adjusted with respect to the rotating axis direction thereof while the hemming roller apparatus 10 moves along the flange 22.

Specifically, following the flowchart described above, it is determined whether or not the torque of the servo motor 141 is larger than the given torque reference value. If it is determined that the torque of the servo motor 141 is larger than the given torque reference value, the position of the hemming roller 12 is adjusted so that the hemming roller 12 projects from the outer housing 15. Namely, the hemming roller 12 is caused to project further from the outer housing 15 by the pushing roller 14, and as shown in FIG. 8, a corner portion between the first tapering surface 122 and the second tapering surface 123 is brought into abutment with the flange 22 of the outer panel 20 so as to press the flange 22.

Accordingly, the hemming roller 12 is positioned in a direction in which the flange 22 is bent largely. A distance between the abutment position of the hemming roller 12 and the bending point A becomes shorter B₂ than the given distance B₁.

According to the exemplary embodiment, the following advantages will be provided.

(1) The deformation resistance of the outer panel 20 can be detected as a load acting on the hemming roller 12 in the axial direction thereof. The deformation resistance is in proportion to the torque of the servo motor 141. Consequently, by adjusting the position of the hemming roller 12 in the rotating axis direction thereof according to the torque by the pushing mechanism 14, the pressing force exerted on the flange 22 by the hemming roller 12 can be changed according to the deformation resistance of the outer panel 20.

Consequently, even if there exists a slight variation in material or height of flanges 22 of outer panels 20 lot by lot, shapes of hemmed flanges 22 of outer panels 20 can be made constant by changing the hemming conditions as required.

In addition, since the distance between the bending point A of the flange 22 and the pressing point of the hemming roller 12 is adjusted by controlling the pushing mechanism 14, the buckling of the outer panel 20 can be prevented.

When the torque detected by the load detection sensor 142 is larger than the torque reference value, the hemming roller 12 is positioned in the direction in which the flange 22 is bent largely. Namely, when the deformation resistance of the outer panel 20 is large, the pressing force exerted on the flange 22 by the hemming roller 12 is increased by adjusting the position of the hemming roller 12 with respect to the rotating axis direction thereof. Consequently, shapes of hemmed flanges 22 of outer panels 20 after hemming can be made constant in an ensured fashion.

The invention is not limited to the exemplary embodiment that has been described heretofore, and modifications and improvements which can attain the object of the invention without departing the spirit and scope of the invention are to be included in the invention.

For example, in the exemplary embodiment, while the riser plane 321 is provided on the die 32 so as to determine the abutment position of the hemming roller 12 with the flange 22, the invention is not limited thereto. For example, the abutment position of the hemming roller 12 with the flange 22 may be determined by controlling the position of the hemming roller 12 with respect to a direction which is perpendicular to the rotating axis direction thereof or providing a stepped portion on the distal end face 121 of the hemming roller 12.

In addition, in the exemplary embodiment, while when the difference calculated by the differential load calculation unit 56 is positive, the position command value calculation unit 57 increases the position command value at all times in proportion to a magnitude of the difference, the invention is not limited thereto. For example, even if the difference calculated is positive, when the magnitude of the difference exceeds a given range, it is determined that the hemming operation should not be allowed, and driving the roller hemming apparatus 10 may be stopped to cease the hemming operation while informing the occurrence of an error. 

1. A roller hemming apparatus for hemming a flange formed on a workpiece, comprising: a main body; a cylindrical roller supported rotatably on the main body; a first position adjusting mechanism for adjusting a first position of the roller with respect to a direction which is perpendicular to a rotating axis direction of the roller; a second position adjusting mechanism for adjusting a second position of the roller with respect to the rotating axis direction; and a control unit for controlling the first position adjusting mechanism and the second position adjusting mechanism, wherein the control unit adjusts the first position of the roller by controlling the first position adjusting mechanism to bring the roller into abutment with a third position which is spaced by a given distance apart from a bending point of the flange, and wherein the control unit adjusts the second position of the roller by detecting a load acting on the roller in an axial direction of the roller as a drive load, calculating a difference between the drive load and a given master load, and controlling the second position adjusting mechanism according to the difference.
 2. The roller hemming apparatus according to claim 1, wherein when the drive load is larger than the master load, the control unit controls the second position adjusting mechanism so as to position the roller in a direction in which the flange is bent largely.
 3. A roller hemming method for hemming a flange formed on a workpiece, comprising: providing a roller hemming apparatus including: a main body; a cylindrical roller supported rotatably on the main body; a first position adjusting mechanism for adjusting a first position of the roller with respect to a direction which is perpendicular to a rotating axis direction of the roller; and a second position adjusting mechanism for adjusting a second position of the roller with respect to the rotating axis direction; adjusting the first position of the roller by controlling the first position adjusting mechanism to bring the roller into abutment with a third position which is spaced by a given distance apart from a bending point of the flange; detecting a load acting on the roller in an axial direction of the roller as a drive load; calculating a difference between the drive load and a given master load; and adjusting the second position of the roller by controlling the second position adjusting mechanism according to the difference.
 4. The roller hemming method according to claim 3, wherein when the drive load is larger than the master load, the roller is positioned in a direction in which the flange is bent largely by controlling the second position adjusting mechanism. 